A dominant part of physiological functions coupled to the blood circulatory system (Table 1.1) is biomechanical in nature. These functions closely depend on influences of biomechanical factors, including different forces (pressure-, shear- and elastic forces) and displacements (flow, shearing, strain). The branch of natural sciences dealing with biomechanical aspects of cardiovascular functions is called haemodynamics. Studying essentials of haemodynamics is crucial for understanding normal physiological functions and pathophysiological alterations of the cardiovascular system. This chapter focuses on the basic principles and characteristics of systemic haemodynamics. Biomechanical properties of the pulmonary circulation and the heart are discussed tangentially only.